speedyxjs
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| posted on 11/3/09 at 07:17 PM |
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Running alternator off driveshaft
In my engine tech lesson today, my tutor was teling us about his mates Matra M630 he is restoring.
As you can see, the alternator is driven off the driveshaft.
Hyperthetically, if an engine was producing around 225hp and you took the alternator off the engine and ran it off the driveshaft, what sort of power
gain might one expect?
How long can i resist the temptation to drop a V8 in?
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Guinness
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| posted on 11/3/09 at 07:23 PM |
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I don't think you'd see any actual increase in performance?
You may gain crank horses, but you'd lose wheel horses? The alterator is sapping power regardless of where it is?
Just my gut feel which may well be completely wrong.
Mike
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iank
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| posted on 11/3/09 at 07:25 PM |
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At the engine a couple of bhp maybe, at the wheels none at all - conservation of energy still having to hold.
Looks like it was done for packaging reasons in that Matra.
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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Stuart_B
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| posted on 11/3/09 at 07:26 PM |
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quote:
Originally posted by Guinness
I don't think you'd see any actual increase in performance?
You may gain crank horses, but you'd lose wheel horses? The alterator is sapping power regardless of where it is?
Just my gut feel which may well be completely wrong.
Mike
those are like my throughts, as you will still be truning the alternator, so causeing drag, and losing power, but i can not be much loss on an engine.
stuart
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blakep82
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| posted on 11/3/09 at 07:27 PM |
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all well and good in a race car which is always moving, but on a road car? nah... 1 traffic jam and a half cut bettery = breakdown
i'd surprised if the benefit was 2hp, if any. more likely none.
i think its like that on the race car to avoid any belts round the front of the engine. can you imagine having to access them on that engine bay? 
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dinosaurjuice
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| posted on 11/3/09 at 07:28 PM |
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at certain speeds it will be less efficient IMO. the engine already has a belt to drive things like water pump. adding another one just for alternator
will only create more drag.
definately for packaging reasons.
edit: maybe it has electric water pump and they wanted to get rid of anything at front altogether.
[Edited on 11/3/09 by dinosaurjuice]
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speedyxjs
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| posted on 11/3/09 at 07:29 PM |
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My thinking was that the rolling mass at the wheels may be big enough that the power lost at the wheels might not be as much as what was gained at the
engine.
How long can i resist the temptation to drop a V8 in?
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BenB
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| posted on 11/3/09 at 07:57 PM |
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The major downside is (as said) a distant lack of charging if you put the clutch down!!! IE for road use you'ld need a flipping great battery to
compensate which would negate any advantage....
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